Wallenberg Syndrome

What Is It, Causes, Diagnosis, Treatment, and More

Author:Maria Villarreal, MD

Editors:Charles Davis, MD,Yifan Xiao, MD,Antonella Melani, MD

Illustrator:Abbey Richard

What is Wallenberg syndrome?

Wallenberg syndrome, also known as “lateral medullary syndrome” or “posterior inferior cerebellar artery (PICA) syndrome”, is the most prevalent posterior ischemic stroke syndrome. Named after Adolf Wallenberg in 1895, this neurological condition is characterized by lateral medullary infarction resulting from an occlusion of the posterior inferior cerebellar artery (PICA) or the vertebral artery. Typically, this is due to an atherothrombotic occlusion, which is when a blood clot blocks one of the arteries that supply the medulla.

Common symptoms include ipsilateral palate weakness, impaired coordination, and contralateral sensory disturbances that involve the contralateral trunk and extremities, and can cause impaired gait and falls. Another frequent finding is Horner syndrome, which is characterized by decreased pupil size, drooping eyelid, and decreased sweating on one side of the body. Other symptoms include dizziness, double vision,  pain or loss of pain on one side of the face, loss of taste on one side of the tongue, difficulty swallowing, slurred speech, and hoarseness. 

What causes Wallenberg syndrome?

The most common cause of Wallenberg syndrome is an ischemic stroke of the brain stem, oftentimes a result from thrombus or embolism. Other less common causes include mechanical trauma to the vertebral artery in the neck, vertebral arteritis (inflammation of the wall of the artery), aneurysm of the vertebral artery, arteriovenous malformations (AVMs), head injury, and multiple sclerosis (MS). 

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What are common risk factors for Wallenberg syndrome?

The most common risk factors for Wallenberg syndrome include hypertension (high blood pressure), smoking, and diabetes. Other, less common, risk factors include connective tissue disorders, such as Marfan syndrome, Ehlers–Danlos syndrome, and fibromuscular dysplasia. In younger people, the most common cause of Wallenberg syndrome is vertebral artery dissection

How is Wallenberg syndrome diagnosed?

Like most ischemic stroke syndromes, initial diagnosis is usually suspected from the patient’s clinical characteristics upon physical examination. 

Physical examination reveals sensory and motor deficits affecting the face and cranial nerves on the ipsilateral (same) side of the infarct. Ataxia, nystagmus, Horner syndrome, and damage to the spinal trigeminal nucleus causes absence of pain and temperature sensation on the ipsilateral side of the face, as well as a diminished corneal reflex.

Patients with a suspected diagnosis should undergo MRI evaluation, including diffusion-weighted imaging, which is the best tool to confirm the infarct in the inferior cerebellar area or lateral medulla.

How is Wallenberg syndrome treated?

The management of Wallenberg syndrome is similar to the management of any acute stroke. Rapid evaluation is an essential component in improving the patient’s clinical outcome and prognosis. The goal of treatment is to reduce the size of infarction and prevent medical complications. Additional long term treatments include speech and swallowing therapies, along with early physical and occupational therapies.

What is the prognosis of someone who has Wallenberg syndrome?

Like other ischemic strokes, the prognosis of a person with Wallenberg syndrome depends on the size and location of the area of the brain stem damaged by the occlusion. Depending on how fast the stroke is treated, some patients may see an improvement in symptoms over weeks or months, while others may be left with significant long term neurological disabilities

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Related links

Posterior blood supply to the brain
Horner's syndrome
Cerebral circulation

Resources for research and reference

Greer, D.M. (2007). Acute Ischemic Stroke: An Evidence-based Approach (1 edition). Hoboken, New Jersey: John Wiley & Sons.

Lui, F., Tadi, P., & Anilkumar, A. C. (2020). Wallenberg Syndrome. In StatPearls. Treasure Island (FL): StatPearls Publishing. Retrieved June 24, 2020, from,

Ruedrich, E. D., Chikkannaiah, M., & Kumar, G. (2016). Wallenberg's Lateral Medullary Syndrome in an Adolescent in American Journal of Emergency Medicine, 34(11):2254.e1-2254.e2. Doi: 10.1016/j.ajem.2016.05.022

Wallenberg Syndrome PICA Syndrome Lateral Medullary Infarction. (2019). In Iowa Head and Neck Protocols. University of Iowa Health Care. Retrieved June 24, 2020, from

Wallenberg’s Syndrome Information Page. (2020). In National Institute of Neurological Disorders and Stroke. Retrieved June 8, 2020, from